1. Field of the Invention
The present invention relates to an engine system for a vessel propulsion device using an engine (internal combustion engine) as a drive source, and a vessel including such an engine system.
2. Description of the Related Art
US 2004/0099237A1 discloses a knocking avoidance control system for a four-stroke engine of an outboard motor. This system includes a knocking sensor that detects an occurrence of knocking of an engine. When the knocking sensor detects knocking, an ignition timing is retarded so as to suppress knocking to a low level. Further, when knocking is suppressed to a predetermined low level, intake air is reduced to keep the low knocking level. By retarding the ignition timing, knocking is suppressed in a short time, and then, by reducing the intake amount, knocking can be suppressed while avoiding deterioration of fuel efficiency.